LN2/LCO2 Expendable Cooling
Liquid Nitrogen Delivery Systems
Expendable coolant chambers use cryogenic LN2 or LCO2 to achieve low temperatures. When coolant is sprayed into the chamber, it immediately evaporates, and in the process, removes heat from the chamber's interior workspace. Therefore, it is essential that liquid is available to the chamber in order for cooling to take place. Liquid Nitrogen boils at -196 °C at 1 atm and has a density of ~ 1.78 lbs/ Liter (50.45 lbs/scf). As LN2 approaches the boiling point of 196 °C, it becomes less efficient at cooling, therefore, chambers configured with the Liquid Nitrogen option as the cooling expectorant have a lower limit of -184 °C. Liquid Nitrogen (LN2) is commonly supplied in either a Dewar or a bulk delivery system. Dewars can be ordered from a local cryogenic supplier. Typical Dewar sizes are 160L (285 lbs), 180L (321 lbs) and 230L (410 lbs). Delivery pressures for an LN2 dewar are available as low (25-50 psi) and high (100 - 230 psi). However, when using an LN2 dewar, it is recommended that you run at the higher delivery pressure (100-230 psi) to ensure that liquid is delivered to the chamber more rapidly and that there is less venting of the dewar. LN2 bulk delivery systems are typically delivered at 25 - 50 psi due to a pressure drop from the long supply line running from the source to the chamber. Because of this, we highly recommend users order their chamber with the LN2 Auto Line Purge option when using running off a bulk supply LN2 delivery system.
Our LN2 chambers come equipped with a 1/2", SAE 45 degree flare male fitting (CGA 295). This is the same fitting that is on the liquid port of a standard LN2 dewar. We recommend using a 1/2" ID, thermally insulated LN2 supply hose to connect from the chamber's valve to the dewar.
LN2 Optional Valves (Available on EC1x, EC1xHA and EC1.3W models)
LN2 Auto Line Purge
For users with long supply lines from a bulk delivery source, we recommend ordering the optional Auto LN2 Line Purge valve. This feature incorporates a second nitrogen valve to purge the supply line of gas to assist in getting liquid nitrogen to the chamber as quickly as possible. This shortens the delay time at the beginning of a cooling cycle when ramping down in temperature.
2-tank LN2 Auto Switch
For users performing extended temperature testing using an LN2 dewar, we offer the 2-tank LN2 Auto Switch valve. The valve has two LN2 inlet fittings to allow for connecting up to two LN2 dewars. When this feature is enabled in the SDEF menu, the controller will automatically switch to the second LN2 tank when the first tank runs out of LN2.
LN2 Redundant Valve
The LN2 redundant valve features a second valve (mechanically in series with the main cooling valve) that will shut down and prevent coolant from entering the chamber and damaging cold sensitive product - in the rare case the main LN2 cooling valve fails in the open position.
N2 Gas Purge
Inherent with expectorant cooled chambers, a dry gas condition exists when cooling since LN2/LCO2 is injected into the chamber. To maintain a dry N2 gas environment for the DUT during heating, the N2 gas purge option can be used. This option consist of a flow meter, needle valve, on/off control valve and a 6 ft. 1/4" OD plastic hose with 1/8" NPT male fitting on both ends. The hose connects from the chamber to the LN2 dewars' N2 gas port (max pressure ~ 100 psi) and can then be turned on using a command entered from the front panel, inserted into a local program temperature profile or sent over the remote interface. We also offer a simpler N2 gas purge without needle valve (manual N2 gas purge). This option consists of a 1/8" NPT brass pipe located on the back of the chamber to allow connection to an N2 gas source.
Liquid Carbon Dioxide Delivery Systems
LCO2 has a boiling point of -78.4°C and is ~ 1.7 lbs/liter at 850psi, 25 °C psi and ~ 2.2 lbs/liter at 300psi, 0 °C. Chambers configured with the Liquid Carbon Dioxide (LCO2) option as the cooling expectorant are able to operate as low as -73 °C. LCO2 is commonly supplied as:
- 50 or 75 lb., 850 psi, K-type siphon cylinder
- 350 lb., 300 psi Dewar ( 180L tank)
- 300 psi bulk delivery satellite system
Our LCO2 chambers come equipped with a 1/8", SAE 37 degree flare male fitting. We supply a 6ft hose and a tank adaptor with a CGA 320 fitting to connect to the tank. This adaptor is also equipped with a 1/8", SAE 37 degree flare male fitting to allow attachment to the LCO2 supply hose. Hoses used with 300 psi LCO2 should be thermally insulated since LCO2 at 300 psi is approximately 0 °C.
LCO2 Optional Valve (Available on EC1x, EC1xHA and EC1.3W models)
3-tank 850 psi LCO2 Auto Switch & 2-tank 300 psi LCO2 Auto Switch Valve
For users performing extended temperature testing using 850psi, LCO2 bottle cylinders - we offer the 3-tank LCO2 Auto Switch Valve. This allows the user to connect 3 LCO2 supply lines to the chamber's valve assembly. When the 3-tank feature is enabled in the SDEF menu, the controller will sense when the cooling rate is low and automatically switch to the next LCO2 tank. The 2-tank assembly is available for those using 300 psi LCO2 dewars.
